Synapses are the sites at which most information processing occurs in the brain. The specificity of synapse formation determines how we feel, move and think; changes in synaptic efficacy underlie learning and memory; most psychoactive drugs target synaptic components; and defects in synapses are .likely to underlie many neurological and psychiatric disease. Until recently however, our understanding of synapses was based largely on a single accessible model synapse, which does not think or learn: the vertebrate skeletal neuromuscular junction. Now, new molecular cellular and genetic tools are making it possible to analyze synapses in the brain with a comparable degree of sophistication. This symposium will cover recent investigations of synapse formation and function in vertebrate peripheral and central nervous systems and in invertebrates, highlighting general principles emerging from studies utilizing diverse systems and techniques. It is one of few small-to-medium sized meetings that cover this important topic in detail, and the fifth in the only established series to focus on synapses. It will be held jointly with a related meeting on hippocampal circuitry, thereby expanding the range of topics that can be covered. Moreover, the two meetings will attract different audiences: molecular/cellular for The Synapse,and systems-oriented for Hippocampus; providing an opportunity for interactions among groups that should be talking more to each other.